Vertically movable air-dam skirts mounted to car bodies by means of stems are mass-produced and sold at present by Alpha Lancia Company for air-flow actuated types and by Nissan Motor Company for motor-protruded types.
Moreover, air-dam skirts of which I am aware are all mounted by stems without any exception, including other several examples exhibited in the Motor Show. These air-dam skirts can be extended downward to a larger size to have higher aerodynamic effects during high-speed runs and retracted to avoid breakage by obstacles on the road surface during low-speed runs.
The air-dam skirt contacts, when lowered, an upper outer plate of the car body so that the air resistance is reduced by preventing the on-coming air from flowing into the inside of the car body.
Therefore, the stem-mounting type capable of lowering the air-dam skirt accurately to a predetermined position with minimum frictional resistance is applied without any exception to the vertically movable type air-dam skirt.
To simplify the structure and minimize production cost, it is desirable to reduce the number of stems and mounted portions. This reduction of mounted portions is exemplified by the mass-produced cars of the front opening type and the protruding type. In the front opening type, the stems are disposed at the back of the air-dam so that the front may be opened. In the protruding type, on the other hand, the stems are disposed in the vicinity of the front nose of the car body so that the air-dam may be protruded from the back. Thus, the mounted portions are located only at the back or front of the air-dam.
When the mounted portions are disposed forwardly of the front wheels, the air-dam is liable to have its rear lower ends come close to the road surface, even if it is raised, and possibly broken when the car is to be parked. This breakage is prevented in the front opening type by positioning the rear portion of the air-dam at a higher level than the front portion when the air-dam is lowered.
Since, in the protruding type, the mounted portions are located in the vicinity of the leading end of the car body, there is no space in the car body for accommodating the raised air-dam in cases where the air-dam extends as far as the sides of the car body. This limits the location of the air-dam to the front of the car body while omitting the air-dam in the space at the body sides from the rear ends of the air-dam to the front wheels so that the air flow undesirably enters through that space onto the bottom of the car body to reduce the lift preventing effect.
The air-dam skirt is intrinsically provided for preventing lift of the car body. Prevention of lift is of greater importance during a turn of the car with a side wind, in which a stronger inertia and lift is exerted upon the car body, than during a straight run.
In case, however, a space is left just forwardly of the front wheels and is not covered with the air-dam, the air flowing obliquely from the front onto the bottom of the car body during the turn of the car with the side wind cannot be blocked to prevent lift of the car body at the most critical time.
In order to minimize the air resistance, on the other hand, it is desirable to cover the fronts of the front wheels up to the positions as low as possible.
Especially in order to minimize the air resistance during the straight run, it is effective for the car body having a tapered front nose that the air-dam skirt extends to low positions up to the fronts of the wheels to cover the front wheels.
It is necessary, for practical purposes, that the air-dam skirt should not be easily broken while the car is running at a low-speed or when parking. The intrinsic object of dropping the air-dam skirt during a high-speed run is to retract it during a low-speed run to thereby prevent its breakage.
In the vertically movable air-dam skirts of the above-specified two types now known, breakage prevention and cost minimization are stressed while leaving the minimization effects of the lift and the air resistance seriously insufficient.
This invention has an object to provide an air-dam having the best aerodynamic and breakage preventing effects at the lowest cost.